Noticed a couple of things playing with this on Ubuntu/Firefox. First, if I happen to hold down shift for the first thing I check, every item from there to the bottom gets selected. I found that surprising. Second the x of y objects selected isn't matching reality when a range is selected. It seems to be counting all the items selected via a shift-click as just one.

Tested with IE8 and Chrome on Windows also. Both also show the behavior of selecting every item to the bottom of the list if shift is held for the first click. Oddly, IE8 counts properly, always reporting how many items are actually selected. Chrome is behaving like Firefox and seeming to count only one item when a shift-click selects multiple.